Single, double and triple deprotonation of a β-diketimine bearing pendant pyridyl group and the corresponding rare-earth metal complexes

Article abstract of DOI:10.1039/b926898g

A new β-diketimine bearing the pendant pyridyl group, CH ₃C(2,6-(ⁱPr)₂C₆H₃NH) CHC(CH₃)(NCH₂-C₅NH₄) (L1), was synthesized. The reaction of L1 with one equivalent of Sc(CH ₂SiMe₃)₃(THF)₂ at room temperature gave a singly deprotonated product (L1-H)Sc(CH₂SiMe₃) ₂ (1). Y(CH₂SiMe₃)₃(THF)₂ under the same conditions led to the unexpected dimer [(L1-H ₃)Y(THF)]₂ (2), in which the ligand precursor L1 was triply deprotonated. The reaction of L1 with Y(CH₂SiMe ₃)₃(THF)₂ at -35°C provided a mixture of singly deprotonated product (L1-H)Y(CH₂SiMe₃)₂ (3) and doubly deprotonated product (L1-H₂)Y(CH₂SiMe ₃)(THF)₂ (4). The reactions of L1 with Ln[N(SiMe ₃)₂]₃ gave only singly deprotonated products (L1-H)Ln[N(SiMe₃)₂]₂ (5: Ln = Y; 6: Ln = La). The complexes 1, 2 and 4-6 have been characterized by single-crystal X-ray diffraction.

Full text of DOI:10.1039/b926898g

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PAPER
www.rsc.org/dalton | Dalton Transactions
Single, double and triple deprotonation of a b-diketimine bearing pendant
pyridyl group and the corresponding rare-earth metal complexes†
Xin Xu,a,b Yaofeng Chen,*b Gang Zou*a and Jie Sunb
Received 22nd December 2009, Accepted 16th February 2010
First published as an Advance Article on the web 16th March 2010
DOI: 10.1039/b926898g
A new b-diketimine bearing the pendant pyridyl group, CH3C(2,6-(iPr)2C6H3NH)CHC(CH3)-
(NCH2–C5NH4) (L1), was synthesized. The reaction of L1 with one equivalent of
Sc(CH2SiMe3)3(THF)2 at room temperature gave a singly deprotonated product (L1-H)Sc(CH2SiMe3)2
(1). Y(CH2SiMe3)3(THF)2 under the same conditions led to the unexpected dimer [(L1-H3)Y(THF)]2
(2), in which the ligand precursor L1 was triply deprotonated. The reaction of L1 with
Y(CH2SiMe3)3(THF)2 at -35 ◦C provided a mixture of singly deprotonated product
(L1-H)Y(CH2SiMe3)2 (3) and doubly deprotonated product (L1-H2)Y(CH2SiMe3)(THF)2 (4). The
reactions of L1 with Ln[N(SiMe3)2]3 gave only singly deprotonated products (L1-H)Ln[N(SiMe3)2]2 (5:
Ln = Y; 6: Ln = La). The complexes 1, 2 and 4–6 have been characterized by single-crystal X-ray
diffraction.
Introduction
Results and discussion
Due to their rich and diverse coordinating properties and reactiv-
ities, organometallic complexes of rare-earth metals have received
great attention.1-3 The most widely investigated organometallic
complexes of rare-earth metals are those bearing Cp-type ligands.
Recently, there is a tendency to explore “non-Cp” rare-earth metal
complexes.4 In this context, ligands with nitrogen donor atoms
have received a growing attention, as they form strong Ln–N
bonds with the hard Ln3+ ions and are expected to stabilize the
highly electrophilic rare-earth metal complexes. One promising
ancillary ligand set of nitrogen containing ligands is the family
of b-diketiminato ligands. Numerous b-diketiminato rare-earth
metal complexes have been reported.5
2-((2,6-Diisopropylphenyl)imido)-2-penten-4-one was prepared
by condensation of acetylacetone with 2,6-diisopropylaniline. This
product was subsequently treated with 2-(aminomethyl)pyridine
in toluene in the presence of a catalytic amount of p-
toluenesulfonic acid, to provide the desired ligand precursor L1
in 61% yield (Scheme 1). It was characterized by NMR (1H, 13C)
and mass spectroscopy and by elemental analysis. Notably, in 1H
NMR spectroscopy of L1 at 25 ◦C, the –CH2– unit of pendant
arm displayed a doublet at 4.32 ppm with a J value of 6.3 Hz due
to the coupling with –NH–, indicating a slow exchange rate of
–NH–. This doublet became a singlet when the temperature rose
to 80 ◦C.
We recently designed a new type of tridentate monoanionic b-
diketiminato ligand with a pendant amino group and prepared
several corresponding rare-earth metal dialkyl complexes.6 As an
extension of our research, we prepared a new b-diketimine deriva-
tive CH3C(2,6-(iPr)2C6H3NH)CHC(CH3)(NCH2–C5NH4) (L1),
which bears a pendant pyridyl group. From reactions of L1 with
LnR3(THF)n (Ln = Sc, Y, La; R = –CH2SiMe3, –N(SiMe3)2; n =
0, 2), we found that this ligand precursor can be singly-, doubly-,
or triply deprotonated depending on the metal ion (Ln3+), the R
group and the reaction conditions.
Scheme 1 Synthesis of the ligand precursor L1.
The reaction of L1 with one equivalent of Sc(CH2SiMe3)3-
(THF)2 in hexane at room temperature for one day gave a
Sc(III) dialkyl complex Sc(L1-H)(CH2SiMe3)2 (1) in 71% yield
(Scheme 2). During the reaction, the ligand precursor L1 was
singly deprotonated, and the resulting ligand L1-H acts as the
monoanionic ligand in the metal complex 1. On the other hand,
the reaction of L1 with one equivalent of Y(CH2SiMe3)3(THF)2
under same conditions provided an unexpected Y(III) dimer
[Y(L1-H3)(THF)]2 (2) in 94% yield (Scheme 2), where L1 was
triply deprotonated to give an unusual trianionic ligand (L1-H3).
The red complex 2 is readily soluble in THF, but nearly insoluble
in benzene, toluene, and hexane. Although the deprotonation of
aLaboratory of Advanced Materials and Institute of Fine Chemicals, East
China University of Science and Technology, 130 Meilong Road, Shanghai,
200237, China. E-mail: zougang@ecust.edu.cn
bState Key Laboratory of Organometallic Chemistry, Shanghai Institute
of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road,
Shanghai, 200032, China; Fax: 86-21-64166128. E-mail: yaofchen@mail.
sioc.ac.cn
† CCDC reference numbers 744083–744085 and 759490–759491. For
crystallographic data in CIF or other electronic format see DOI:
10.1039/b926898g
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a release of SiMe4. Then the intensity of the signals belonging
to 3 gradually decreased while that of SiMe4 increased with
time, and a red precipitate 2 formed. After 24 h, the signals
of 3 had disappeared. No signals belonging to 4 were observed
during the process. These results were consistent with the former
observation and suggested that 3 was produced first through a
single deprotonation of L1, and the doubly deprotonated product
4 was very instable and immediately converted to the triply
deprotonated product at room temperature.
Single crystals of 1, 4 and 2 were characterized by X-ray
diffraction, and the molecular structures are shown in Fig. 1, 2
and 3, respectively. 1 is a solvent-free, five-coordinate monomer.
The monoanionic ligand L1-H serves as one tridentate ligand and
the five-coordinate center is completed by a pair of –CH2SiMe3
substituents. The geometry at the metal ion is best described as
distorted square pyramidal, the metal ion sits out of the N1-N2-
˚
N3-C26 plane 0.68 A, and one of the –CH2SiMe3 substituents
takes the apical position. The C–N and C–C bond lengths of the
Scheme 2 Reactions of L1 with Ln(CH2SiMe3)3(THF)2 (Ln = Sc, Y).
the methyl group of the monoanionic b-diketiminato ligand7 and
the deprotonation of the methyl group attached to the pyridyl
ring8 have been documented, such triple deprotonation of a ligand
precursor to a trianionic ligand as in our case is interesting.
It has been commonly accepted that the alkyl complexes of
larger rare-earth metal ions are less stable than those of the
smaller,9 and it’s also known that the complexes are generally
more stable at low temperature. Thus, the reaction of L1 with
◦
Y(CH2SiMe3)3(THF)2 was carried out in hexane at -35 C, and
a dark green product precipitated from the reaction solution.
From this experiment, several single crystals were collected and
characterized by X-ray diffraction, which showed them to belong
to 4, a Y(III) monoalkyl complex Y(L1-H2)(CH2SiMe3)(THF)2 (4)
containing the dianionic ligand (L1-H2), in which the methylene
group on the pendant arm was deprotonated. The product was
then dissolved in C6D6 for NMR analysis. The C6D6 solution
was clear at the beginning, but a red precipitate 2 formed in two
minutes. The 1H NMR spectrum clearly showed the existence
of 3, a Y(III) dialkyl complex Y(L1-H)(CH2SiMe3)2 containing
the monoanionic ligand (L1-H). This showed that the singly
deprotonated product and the doubly deprotonated product could
be achieved at low temperature. Surprisingly, no signals for 4
were observed, but a strong signal of SiMe4 was observed, and
in consistency with the formation of SiMe4, the signals for 2 were
Fig. 1 Molecular structure of complex 1. The hydrogen atoms are omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): Sc–N1 2.198(2),
Sc–N2 2.198(2), Sc–N3 2.308(2), Sc–C22 2.197(3), Sc–C26 2.254(2),
C1–C2 1.504(4), C2–C3 1.396(4), C3–C4 1.381(4), C4–C5 1.519(4), C2–N1
1.326(3), C4–N2 1.326(3), N2–C6 1.461(3), C6–C7 1.478(4), C7–N3
1.333(3), C8–N3 1.344(4), ∠N2–C6–C7 113.1(2).
1
observed in the H NMR spectrum. These observations suggest
that 4 is unstable in solution at room temperature and quickly
transforms into 2 with a release of SiMe4. It was also observed
that the intensity of the 1H NMR signals of 3 gradually decreased
while that due to SiMe4 increased with time, and the amount of
the red precipitate 2 increased with time. 3 had nearly completely
changed into 2 after 24 h. To gain further information on the
formation of 4, 1H NMR spectral monitoring of the reaction
of L1 with Y(CH2SiMe3)3(THF)2 at room temperature in C6D6
was also performed. The spectra indicated the nearly quantitative
formation of the dialkyl complex 3 within ten minutes along with
Fig. 2 Molecular structure of complex 4. The hydrogen atoms are omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): Y–N1 2.310(4), Y–N2
2.423(4), Y–N3 2.346(4), Y–C22 2.406(5), Y–O1 2.363(4), Y–O2 2.400(4),
C1–C2 1.533(7), C2–C3 1.353(7), C3–C4 1.433(7), C4–C5 1.506(7), C2–N1
1.372(6), C4–N2 1.324(6), N2–C6 1.393(6), C6–C7 1.373(7), C7–N3
1.390(6), C8–N3 1.344(7), ∠N2–C6–C7 120.9(5).
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plane. These structural data demonstrate the electronic delocalized
structure of NCH–C5NH4(pyridyl). The distance from the metal
˚
ion to the nitrogen atom on the pyridyl group in 4 is 2.346(4) A,
˚
which is close to the average Y–N(imine) distance (2.36 A) in the
same complex.
2 exists as a centrosymmetric dimer, and each metal ion is
coordinated by one trianionic ligand L1-H3, one THF molecule,
and the C5-C4-N2-C6 unit of another L1-H3, which acts as
a bridge. The geometry at the metal ions can be described
as distorted square pyramidal when the C5-C4-N2-C6 unit is
regarded as occupying a single polyhedral vertex. The metal ion
˚
sits out of the N1-N2-N3-O1 plane by 0.92 A, and the C5-C4-N2-
C6 unit takes the apical position. As observed in 4, the backbone of
L1-H3 coordinates to the metal ion with two unequal Y–N(imine)
˚
bonds (2.298(3) and 2.336(3) A). The Y–N3 bond length in 2,
Fig. 3 Molecular structure of complex 2. The hydrog◦en atoms are omitted
˚
˚
2.394(4) (A), is slightly longer than that in 4, 2.346(4) A. The
˚
for clarity. Selected bond lengths (A) and angles ( ): Y1–N1 2.298(3),
distances from the metal ion to C5, C4, N2 and C6 atoms of
Y1–N2 2.336(3), Y1–N3 2.394(4), Y1–O1 2.425(3), Y1–C4A 2.688(4),
Y1–C5A 2.698(4), Y1–C6A 2.540(4), Y1–N2A 2.488(3), Y1–Y1A
3.6939(9), C1–C2 1.525(6), C2–C3 1.331(6), C3–C4 1.428(6), C4–C5
1.402(6), C2–N1 1.397(6), C4–N2 1.360(5), N2–C6 1.435(5), C6–C7
1.397(6), C7–N3 1.383(6), C8–N3 1.352(6), ∠N2–C6–C7 116.1(4). The
‘A’ denoted atoms are at symmetrically equivalent positions (1 - x, 2 - y,
1 - z).
˚
the other L1-H3 are 2.698(4), 2.688(4), 2.488(3) and 2.540(4) A,
˚
respectively, the average Y–C distance (2.64 A) is close to that in
10
˚
˚
[(C5H5)2YCl]2 (2.60 A). The Y–Y separation (3.69 A) indicates
that there is no bonding interaction between the two metal ions.
L1-H3 shows some similar character to L1-H2, for example, the
˚
C6–C7 bond length (1.397(6) A) is intermediate between those
of typical single and double bonds and the N3–C7 bond length
˚
b-diketiminato backbone are intermediate between those of
typical single and double bonds, and the N1, C2, C3, C4 and N2
atoms are coplanar, indicating a delocalized electronic structure.
The b-diketiminato backbone coordinates to the metal ion in
bidentate s, s’-bonded fashion; the Sc–N1 and Sc–N2 bond
(1.383(6) A) is longer than that in 1. However, differences between
L1-H3 and L1-H2 are also significant. The C4–C5 bond length
˚
˚
(1.402(6) A) in 2 is much shorter than that in 4 (1.506(7) A) and is
intermediate between those of typical single and double bonds, and
the ∠C3–C4–C5 in 2 (119.8(4)◦) is larger than that in 4 (115.9(5)◦).
1
˚
lengths are both 2.198(2) A, while the distances from the metal
In the H NMR spectra of complexes 1 and 3, the signals for
ion to the carbon atoms C2, C3 and C4 are too long for effective
Py-Ha (8.89 ppm for both complexes) are shifted downfield in
comparison to that of the ligand precursor (8.34 ppm), indicating
that the coordination interaction between the metal ion and the
pendant pyridyl group is retained in solution.11 The signals for the
–CH2– unit of the pendant arm in 1 and 3 are singlets, which is in
contrast to the ligand precursor and consistent with deprotonation
of the ligand precursor. Distinct differences between the trianionic
ligand L1-H3 in 2 and the monoanionic ligand L1-H in 3 were
˚
interaction (> 3.13 A). The pyridyl group coordinates to the metal
˚
ion with a Sc–N3 bond length of 2.308(2) A, which is longer than
˚
the Sc–N(imine) bond length (2.198(2) A), implying the pendant
arm acts as a neutral donor while the backbone is an anionic
donor.
4 is a six-coordinate monomer, in which the metal ion is
coordinated by one dianionic ligand L1-H2, one –CH2SiMe3
substitutent, and two THF molecules. The geometry at the metal
ion is distorted octahedral, the metal ion lies in the N1-N2-N3-C22
plane, and two THF molecules occupy the axial positions. Both
THF molecules are bent towards the b-diketiminato backbone to
avoid steric repulsion with the bulky 2,6-(iPr)2-C6H3 substituent.
In contrast to the two equal metal–N(imine) bonds in 1, one Y–
1
observed from the H NMR spectra. L1-H3 has a –CH2– unit
from deprotonation of the methyl group on the backbone, which
contains two diastereotopic protons and displays two singlets at
2.37 and 2.58 ppm. 2JHH coupling was not observed for these two
protons, which is probably due to a very small coupling constant in
contrast to those of the reported Sc and Ca complexes containing
similar dianionic ligands.7b,c Furthermore, the 1H NMR spectra of
2 showed that L1-H3 has a –CH– unit on the pendant arm.
As L1 was triply deprotonated during its reaction with
Y(CH2SiMe3)3(THF)2 at room temperature, it was worth checking
if this could also be achieved by employing the yttrium amide
Y[N(SiMe3)2]3. The experiment showed that treatment of ligand
precursor L1 with one equivalent of Y[N(SiMe3)2]3 in hexane at
room temperature gave the yttrium bis(amide) 5 in 75% yield
(Scheme 3), which contains the monoanionic ligand (L1-H).
Furthermore, the reaction of L1 with La[N(SiMe3)2]3 at room
temperature also gave the singly deprotonated product 6 in 71%
yield. Complexes 5 and 6 were both characterized by NMR
spectroscopy (1H, 13C) and elemental analyses.
˚
N(imine) bond in 4 (Y–N2 = 2.423(4) A) is significantly longer
˚
than the other (Y–N1 = 2.310(4) A). Similarly, the C(imine)–
N(imine) bonds and C3–C(imine) bonds in 4 are unequal,
˚
˚
˚
˚
1.372(6) A vs. 1.324(6) A and 1.353(7) A vs. 1.433(7) A, while 1 has
equal C(imine)–N(imine) bonds and similar C3–C(imine) bonds.
A distinguished structural difference between L1-H2 and L1-H
lies in the pendant arm. The N2–C6 and C6–C7 bond lengths in
˚
4 (1.393(6) and 1.373(7) A) are significantly shorter than those in
˚
1 (1.461(3) and 1.478(4) A) and are intermediate between those
of typical single and double bonds, furthermore the ∠N2–C6–C7
in 4 (120.9(5)◦) is larger than that in 1 (113.1(2)◦). The N3–C7
˚
˚
bond length in 4 (1.390(6) A) is longer than that in 1 (1.333(3) A),
while the N3–C8 bond lengths in these two complexes are same
˚
˚
(1.344(7) A in 4 and 1.344(4) A in 1). The N2, C6, C7 and N3 atoms
in 4 are coplanar, and the plane is nearly planar with the pyridine
Single crystals of 5 and 6 were grown from hexane solutions at
-35 C and characterized by X-ray diffraction. Their molecular
◦
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out of the above plane. The dihedral angles between the C2-
C3-C4 plane and N1-C2-C4-N2 plane in 5 and 6 are 23.2◦ and
25.0◦, respectively, which are significantly larger than that in the
dialkyl complex 1 (10.5◦). The deviation values of the metal ion
˚
˚
from the N1-C2-C4-N2 plane in 5 and 6 (1.53 A and 1.82 A) are
˚
significantly larger than that in 1 (0.70 A), if the differences in
Ln3+ radii are taken into account. In addition, the distances from
the metal ion to the carbon atoms on the backbone are rather
Scheme 3 Reactions of L1 with Ln[N(SiMe3)2]3 (Ln = Y, L a ) .
˚
˚
short (3.04 ~ 3.19 A in 5 and 3.02 ~ 3.18 A in 6) and the difference
between these distances is not significant. These structural features
5
structures are shown in Fig. 4 and 5, respectively. 5 and 6 are
both five-coordinate monomers and the metal ions adopt distorted
square pyramidal geometry. The monoanionic ligand L1-H serves
as a tridentate ligand and a pair of –N(SiMe3)2 substituents
complete the coordination sphere. Atoms N1, C2, C4 and N2
of the backbone are coplanar, but the central atom C3 is bent
indicated a tendency for an h bonding pattern between the metal
ion and the b-diketiminato backbone, especially in 6.12 Although
5 and 6 contain bulky –N(SiMe3)2 ligands, the metal ions of
both complexes are coordinated by the pendant arms (Ln–N3
1
˚
˚
2.502(3) A for 5 and 2.682(5) A for 6). The H NMR spectra of
5 and 6 show some similarities to those of 1 and 3 in that the
signals for Py-Ha (9.44 ppm for 5 and 9.36 ppm for 6) are shifted
downfield in comparison to in the ligand precursor and the signals
for the –CH2– unit of the pendant arm are singlets.
Conclusions
A
new b-diketimine derivative CH3C(2,6-(iPr)2C6H3NH)-
CHC(CH3)(NCH2–C5NH4) (L1), which bears a pendant pyridyl
group, was prepared. This ligand precursor reacted with
LnR3(THF)n (Ln = Sc, Y, La; R = –CH2SiMe3, –N(SiMe3)2; n = 0,
2)togivethesinglydeprotonatedproducts(L1-H)Ln(CH2SiMe3)2
(Ln = Sc, Y) and (L1-H)Ln[N(SiMe3)2]2 (Ln = Y, La), the
doubly deprotonated product (L1-H2)Y(CH2SiMe3)(THF)2, and
the triply deprotonated product [(L1-H3)Y(THF)]2. How far the
deprotonations proceed depends on the reaction temperature, the
rare-earth metal ion and the R group. The di-, and trianionic
ligands represent new multidentate ligands.
Fig. 4 Molecular structure of complex 5. The hydrogen atoms are omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): Y–N1 2.375(3), Y–N2
2.308(3), Y–N3 2.502(3), Y–N4 2.297(3), Y–N5 2.288(3), C1–C2 1.503(5),
C2–C3 1.392(5), C3–C4 1.406(6), C4–C5 1.505(5), C2–N1 1.338(5), C4–N2
1.305(5), N2–C6 1.463(5), C6–C7 1.484(6), C7–N3 1.346(5), C8–N3
1.347(5), ∠N2–C6–C7 112.0(3).
Experimental
General procedures
All operations were carried out under an atmosphere of argon
using standard Schlenk techniques or in a nitrogen gas filled
glovebox. Toluene and hexane were dried over Na/K alloy. C6D6
and THF-d8 were purchased from Cambridge Isotopes, dried over
Na/K alloy, distilled under vacuum and stored in the glovebox.
2-(Aminomethyl)pyridine was purchased from Acros and used
without further purification. 2-(2,6-Diisopropylphenylimido)-2-
pentene-4-one,13 Ln(CH2SiMe3)3(THF)2 (Ln = Sc, Y)14 and
Ln[N(SiMe3)2]3 (Ln = Y, L a ) 15 were synthesized following the
1
literature procedures. H and 13C NMR spectra were recorded
on a Varian Mercury 300 or 400 spectrometer, and the chemical
shifts were reported in d (ppm) units with reference to the residual
solvent resonance of the deuterated solvents. Elemental analysis
was performed by Analytical Laboratory of Shanghai Institute
of Organic Chemistry. Melting points of the complexes were
determined on a Digital Melting Point Apparatus SWG X-4 in
a sealed capillary and are uncorrected.
Fig. 5 Molecular structure of complex 6. The hydrogen atoms are omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): La–N1 2.553(5),
La–N2 2.428(5), La–N3 2.682(5), La–N4 2.441(5), La–N5 2.428(5), C1–C2
1.524(9), C2–C3 1.392(9), C3–C4 1.386(10), C4–C5 1.514(10), C2–N1
1.311(8), C4–N2 1.329(9), N2–C6 1.450(8), C6–C7 1.482(11), C7–N3
1.335(9), C8–N3 1.349(10), ∠N2–C6–C7 110.8(6).
L1. 2-(2,6-Diisopropylphenylimido)-2-pentene-4-one (5.62 g,
21.6 mmol), 2-(aminomethyl)pyridine (2.61 g, 24.1 mmol), and
a catalytic amount of p-toluenesulfonic acid in toluene (30 mL)
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3
3
were combined and heated at reflux overnight. H2O produced
during the reaction was removed as a toluene azeotrope using
a water separator. The toluene was removed in vacuo after the
reaction was completed, and the residue was dissolved in 20 mL
of ether. The ether solution was washed with saturated aqueous
Na2CO3 3 times, and then the volatiles were removed in vacuo.
Recrystallization of the crude product from hexane gave L1 as a
pale yellow solid (4.62 g, 61% yield). 1H NMR (300 MHz, C6D6,
1.28 (d, JHH = 6.9 Hz, 6H, ArCHMe2), 0.99 (d, JHH = 6.9 Hz,
3
6H, ArCHMe2), 0.98 ppm (d, JHH = 6.9 Hz, 6H, ArCHMe2).
13C NMR (75 MHz, THF-d8, 25 ◦C): d = 166.7, 159.1, 152.0,
149.7, 145.9, 145.0, 132.4, 124.1, 123.8, 117.9, 106.5 (imine-C,
Ar-C, and Py-C), 101.6 (MeC(N)CH), 68.2 (THF), 60.7 (NCH),
28.3 (ArCHMe2), 28.1 (ArCHMe2), 26.6 (CH2), 26.4 (THF), 25.3
(overlapped with THF-d8 signals, ArCHMe2), 25.1 (ArCHMe2),
24.1 ppm (MeC). Elemental analysis (%) calcd for C54H72N6O2Y2:
C 63.90, H 7.15, N 8.28; found: C 63.59, H 7.55, N 7.83. m. p.
>300 ◦C.
◦
3
25 C): d = 11.50 (br, 1H, NH), 8.34 (d, JHH = 4.2 Hz, 1H,
Py-H), 7.18–7.02 (m, 5H, Py-H and Ar-H), 6.52 (m, 1H, Py-H),
3
4.70 (s, 1H, MeC(N)CH), 4.32 (d, JHH = 6.3 Hz, 2H, NCH2),
A
mixture of (L1-H)Y(CH2SiMe3)2 (3) and (L1-H2)-
3.14 (sp, 3JHH = 6.9 Hz, 2H, ArCHMe2), 1.64 (s, 3H, MeC), 1.61
(s, 3H, MeC), 1.20 (d, 3JHH = 6.9 Hz, 6H, ArCHMe2), 1.14 ppm
Y(CH2SiMe3)(THF)2 (4). L1 (120 mg, 0.34 mmol) in 2 mL of
hexane was added to Y(CH2SiMe3)3(THF)2 (168 mg, 0.34 mmol)
in 5 mL of hexane at -35 ◦C. The color of the reaction
mixture gradually changed to green. After standing at -35 ◦C
for 24 h, a dark green product precipitated from the solution.
The supernatant liquid was removed, 125 mg dark green crystals
were obtained. 1H NMR of 3 (300 MHz, C6D6, 25 ◦C): d = 8.89
3
(d, JHH = 6.9 Hz, 6H, ArCHMe2). 13C NMR (75 MHz, C6D6,
25 ◦C): d = 166.8, 160.4, 155.6 (imine-C and Py-C), 149.6, 147.3,
138.2, 136.3, 123.5, 123.2, 121.7, 120.3 (Ar-C and Py-C), 94.9
(MeC(N)CH), 48.9 (NCH2), 28.5 (ArCHMe2), 24.1 (ArCHMe2),
23.1 (ArCHMe2), 21.8 (MeC), 19.1 ppm (MeC). EIMS m/z 349
(M+, 60.25), 133 (100). Elemental analysis (%) calcd for C23H31N3:
C 79.04, H 8.94, N 12.02; found: C 78.67, H 8.72, N 12.13. m. p.
76–78 ◦C.
3
(d, JHH = 5.1 Hz, 1H, Py-H), 7.17 (m, 3H, Ar-H), 6.83 (td,
3JHH = 7.8 Hz and JHH = 1.6 Hz, 1H, Py-H), 6.51 (t, JHH
=
4
3
6.0 Hz, 1H, Py-H), 6.38 (d, 3JHH = 8.1 Hz, 1H, Py-H), 4.97 (s, 1H,
3
(L1-H)Sc(CH2SiMe3)2 (1). L1 (70 mg, 0.20 mmol) in 2 mL of
hexane was added to Sc(CH2SiMe3)3(THF)2 (90 mg, 0.20 mmol)
in 3 mL of hexane at room temperature. The reaction mixture
was stirred at room temperature for 24 h and filtered. The filtrate
was concentrated to approximately 2 mL and cooled to -35 ◦C
to afford 1 as a pale green crystalline solid (80 mg, 71% yield).
Single crystals of 1 suitable for X-ray diffraction were obtained
from a toluene solution. 1H NMR (400 MHz, C6D6, 25 ◦C): d =
8.89 (d, 3JHH = 5.6 Hz, 1H, Py-H), 7.21 (m, 3H, Ar-H), 6.88 (td,
MeC(N)CH), 4.47 (s, 2H, NCH2), 3.37 (sp, JHH = 6.8 Hz, 2H,
ArCHMe2), 1.81 (s, 3H, MeC), 1.70 (s, 3H, MeC), 1.43 (d, 3JHH
=
6.9 Hz, 6H, ArCHMe2), 1.20 (d, 3JHH = 6.9 Hz, 6H, ArCHMe2),
2
2
0.10 (s, 18H, SiMe3), -0.40 (dd, JHH = 10.2 Hz, JYH = 2.7 Hz,
2
2
2H, CH2SiMe3), -0.49 (dd, JHH = 10.2 Hz, JYH = 2.7 Hz, 2H,
CH2SiMe3).
(L1-H)Y[N(SiMe3)2]2 (5). Following the procedure described
for 1, reaction of L1 (78 mg, 0.22 mmol) with Y[N(SiMe3)2]3
(128 mg, 0.22 mmol) gave 5 as a colorless crystalline solid (125 mg,
4
3
3JHH = 7.8 Hz and JHH = 1.6 Hz, 1H, Py-H), 6.57 (t, JHH
=
75% yield). 1H NMR (400 MHz, C6D6, 25 ◦C): d = 9.44 (d, 3JHH
=
6.8 Hz, 1H, Py-H), 6.43 (d, 3JHH = 8.0 Hz, 1H, Py-H), 5.05 (s, 1H,
5.2 Hz, 1H, Py-H), 7.11 (m, 3H, Ar-H), 6.91 (td, 3JHH = 7.6 Hz and
4JHH = 1.6 Hz, 1H, Py-H), 6.67 (t, 3JHH = 6.4 Hz, 1H, Py-H), 6.51
(d, 3JHH = 8.0 Hz, 1H, Py-H), 5.08 (s, 1H, MeC(N)CH), 4.57 (s,
2H, NCH2), 3.16 (br, 2H, ArCHMe2), 1.88 (s, 3H, MeC), 1.75 (s,
3
MeC(N)CH), 4.48 (s, 2H, NCH2), 3.51 (sp, JHH = 6.8 Hz, 2H,
ArCHMe2), 1.80 (s, 3H, MeC), 1.75 (s, 3H, MeC), 1.49 (d, 3JHH
=
6.8 Hz, 6H, ArCHMe2), 1.20 (d, 3JHH = 6.8 Hz, 6H, ArCHMe2),
0.11 (s, 4H, CH2SiMe3), -0.02 ppm (s, 18H, SiMe3). 13C NMR
(100 MHz, C6D6, 25 ◦C): d = 167.7, 164.9, 161.1 (imine-C and
Py-C), 149.8, 146.8, 142.9, 139.1, 126.4, 124.8, 122.3, 121.8 (Ar-C
and Py-C), 99.4 (MeC(N)CH), 57.3 (NCH2), 40.4 (br, CH2SiMe3),
28.8 (ArCHMe2), 25.5 (ArCHMe2), 25.2 (ArCHMe2), 24.9 (MeC),
23.6 (MeC), 4.2 ppm (SiMe3). Elemental analysis (%) calcd for
C31H52N3Si2Sc: C 65.56, H 9.23, N 7.40; found: C 64.86, H 8.88,
N 7.32. m. p. 125–127 ◦C.
3H, MeC), 1.39 (d, 3JHH = 6.8 Hz, 6H, ArCHMe2), 1.10 (d, 3JHH
=
6.4 Hz, 6H, ArCHMe2), 0.21 ppm (s, 36H, SiMe3). 13C NMR
(100 MHz, C6D6, 25 ◦C): d = 166.7, 162.1, 161.7 (imine-C and Py-
C), 152.1, 147.4, 142.8, 138.7, 125.2, 124.1, 121.4, 121.3 (Ar-C and
Py-C), 97.9 (MeC(N)CH), 55.9 (NCH2), 27.9 (ArCHMe2), 25.4
(ArCHMe2), 25.3 (ArCHMe2), 24.3 (MeC), 21.5 (MeC), 6.1 ppm
(SiMe3). Elemental analysis (%) calcd for C35H66N5Si4Y: C 55.45,
H 8.77, N 9.24; found: C 55.58, H 8.78, N 9.13. m. p. 165–167 ◦C.
[(L1-H3)Y(THF)]2 (2). L1 (70 mg, 0.20 mmol) in 2 mL of
hexane was added to Y(CH2SiMe3)3(THF)2 (100 mg, 0.20 mmol)
in 3 mL of hexane at room temperature. The color of reaction
mixture immediately changed to dark green. After standing at
room temperature for 24 h, a red product precipitated from the
solution. The supernatant liquid was removed and 2 was obtained
as red crystals (95 mg, 94% yield). 2 is nearly insoluble in toluene
and benzene, but soluble in THF. 1H NMR (300 MHz, THF-d8,
25 ◦C): d = 7.46 (d, 3JHH = 5.7 Hz, 2H, Py-H), 7.14 (m, 2H, Ar-H),
(L1-H)La[N(SiMe3)2]2 (6). Following the procedure de-
scribed for 1, reaction of L1 (70 mg, 0.20 mmol) with
La[N(SiMe3)2]3 (124 mg, 0.20 mmol) gave 6 as a pale red crystalline
solid (115 mg, 71% yield). 1H NMR (400 MHz, C6D6, 25 ◦C): d =
9.36 (d, 3JHH = 5.2 Hz, 1H, Py-H), 7.10 (m, 3H, Ar-H), 6.90 (td,
4
3
3JHH = 7.6 Hz and JHH = 1.6 Hz, 1H, Py-H), 6.66 (t, JHH
=
3
6.6 Hz, 1H, Py-H), 6.53 (d, JHH = 8.0 Hz, 1H, Py-H), 5.03 (s,
1H, MeC(N)CH), 4.64 (br, 2H, NCH2), 3.08 (br, 2H, ArCHMe2),
1.94 (s, 3H, MeC), 1.75 (s, 3H, MeC), 1.36 (br, 6H, ArCHMe2),
1.10 (br, 6H, ArCHMe2), 0.21 ppm (s, 36H, SiMe3). 13C NMR
(75 MHz, C6D6, 25 ◦C): d = 164.6, 162.9, 159.8 (imine-C and
Py-C), 151.3, 146.8, 141.6, 138.6, 125.2, 124.1, 121.7, 121.6 (Ar-C
and Py-C), 93.3 (MeC(N)CH), 57.6 (NCH2), 28.4 (ArCHMe2),
25.1 (ArCHMe2), 24.9 (MeC), 24.7 (br, ArCHMe2), 22.1 (MeC),
3
6.96 (m, 4H, Ar-H), 6.63 (t, JHH = 7.4 Hz, 2H, Py-H), 6.30 (d,
3JHH = 8.4 Hz, 2H, Py-H), 5.68 (t, 3JHH = 6.0 Hz, 2H, Py-H), 4.35
(s, 2H, MeC(N)CH), 4.01 (s, 2H, NCH), 3.79 (sp, 3JHH = 6.9 Hz,
2H, ArCHMe2), 3.60 (m, 8H, THF), 3.17 (sp, 3JHH = 6.8 Hz, 2H,
ArCHMe2), 2.58 (s, 2H, CH2), 2.37 (s, 2H, CH2), 1.76 (m, 8H,
THF), 1.53 (d, 3JHH = 6.9 Hz, 6H, ArCHMe2), 1.37 (s, 6H, MeC),
3956 | Dalton Trans., 2010, 39, 3952–3958
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Table 1 Crystallographic Data and Refinement for Complexes 1, 2 and 4–6
1
2
4
5
6
Formula
fw
Color
C31H52N3Si2Sc
567.90
Colorless
Triclinic
¯
P1
C54H72N6O2Y2
1015.00
Red
Triclinic
¯
P1
C35H56N3O2SiY
667.83
Black
Monoclinic
P21/c
9.6283(18)
18.118(3)
21.637(4)
90
100.217(4)
90
3714.5(12)
4
1.194
C35H66N5Si4Y
758.20
Colorless
Monoclinic
P21/c
20.1051(19)
12.0332(11)
18.0092(18)
90
93.836(2)
90
4347.2(7)
4
1.158
1624
1.97–27.00
25104
C35H66N5Si4La
808.20
Colorless
Triclinic
¯
P1
Cryst.syst
Space group
˚
a/A
9.6221(12)
10.3910(12)
18.515(2)
77.516(2)
81.161(2)
72.257(2)
1713.7(4)
2
1.101
616
2.19–26.00
9448
6612
10.2136(13)
11.1187(14)
13.3747(17)
68.788(2)
84.920(2)
65.451(2)
1284.5(3)
1
1.312
532
1.64–26.00
7104
4972
10.6794(18)
11.7544(19)
18.051(3)
85.938(3)
86.272(3)
81.210(3)
2230.4(6)
2
1.203
848
1.76–25.50
11582
8145
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
V/A
Z
Dc/g cm-3
F(000)
1424
1.91–25.50
18865
6889
3109
q range, (◦)
No. of reflns collected
No. of unique reflns
No. of obsd reflns(I > 2s(I))
No.of params
9469
4561
424
4520
346
3457
294
6860
424
378
Goodness of fit
Final R, Rw(I > 2s(I))
Drmax,min/e A
0.945
0.0540, 0.1190
0.382, -0.231
0.948
0.0483, 0.1041
0.466, -0.414
0.885
0.0583, 0.1308
0.753, -0.555
0.937
0.0508, 0.1068
0.774, -0.463
1.030
0.0654, 0.1587
3.449, -1.292
-3
˚
5.4 ppm (SiMe3). Elemental analysis (%) calcd for C35H66N5Si4La:
C 52.01, H 8.23, N 8.67; found: C 52.63, H 7.98, N 8.38. m. p.
197–199 ◦C.
(c) W. J. Evans and B. L. Davis, Chem. Rev., 2002, 102, 2119; (d) W. J.
Evans, Inorg. Chem., 2007, 46, 3435.
2 (a) G. A. Molander and J. A. C. Romero, Chem. Rev., 2002, 102,
2161; (b) S. Hong and T. J. Marks, Acc. Chem. Res., 2004, 37,
673.
3 (a) H. Yasuda, J. Organomet. Chem., 2002, 647, 128; (b) Z. Hou
and Y. Wakatsuki, Coord. Chem. Rev., 2002, 231, 1; (c) J. Gromada,
J. F. Carpentier and A. Mortreux, Coord. Chem. Rev., 2004, 248,
397.
4 (a) F. T. Edelmann, D. M. M. Freckmann and H. Schumann, Chem.
Rev., 2002, 102, 1851; (b) W. E. Piers and D. J. H. Emslie, Coord.
Chem. Rev., 2002, 233–234, 131; (c) V. C. Gibson and S. K. Spitzmesser,
Chem. Rev., 2003, 103, 283.
5 L. Bourget-Merle, M. F. Lappert and J. R. Severn, Chem. Rev., 2002,
102, 3031.
6 X. Xu, X. Y. Xu, Y. F. Chen and J. Sun, Organometallics, 2008, 27,
758.
7 (a) Y. Ding, H. Hao, H. W. Roesky, M. Noltemeyer and H.-G. Schmidt,
Organometallics, 2001, 20, 4806; (b) A. M. Neculai, H. W. Roesky, D.
Neculai and J. Magull, Organometallics, 2001, 20, 5501; (c) S. Harder,
Angew. Chem., Int. Ed., 2003, 42, 3430; (d) F. Basuli, J. C. Huffman
and D. J. Mindiola, Inorg. Chem., 2003, 42, 8003; (e) S. Harder, Angew.
Chem., Int. Ed., 2004, 43, 2714; (f) P. B. Hitchcock, M. F. Lappert
and A. V. Protchenko, Chem. Commun., 2005, 951; (g) F. Basuli, J. C.
Huffman, B. C. Bailey and D. J. Mindiola, Organometallics, 2005, 24,
3321; (h) S. T. Liddle and P. L. Arnold, Dalton Trans., 2007, 3305;
(i) S. Bambirra, F. Perazzolo, S. J. Boot, T. J. J. Sciarone, A. Meetsma
and B. Hessen, Organometallics, 2008, 27, 704; (j) A. Jana, C. Schulzke
and H. W. Roesky, J. Am. Chem. Soc., 2009, 131, 4600; (k) A. Jana,
I. Objartel, H. W. Roesky and D. Stalke, Inorg. Chem., 2009, 48,
7645.
X-ray Crystallography
Suitable single crystals of 1, 2 and 4–6 were sealed in thin-walled
glass capillaries, and data collection was performed at 20 C on
a Bruker SMART diffractometer with graphite-monochromated
Mo-Ka radiation (l = 0.71073 A). The SMART program package
◦
˚
was used to determine the unit-cell parameters. The absorption
correction was applied using SADABS. The structures were solved
by direct methods and refined on F2 by full-matrix least squares
techniques with anisotropic thermal parameters for non-hydrogen
atoms. Hydrogen atoms were placed at calculated positions
and were included in the structure calculation without further
refinement of the parameters. All calculations were carried out
using the SHELXS-97 program. The software used is listed in the
references.16-20 Crystallographic data and refinement are given in
Table 1.
Acknowledgements
This work was supported by the National Natural Science Foun-
dation of China (Grant Nos. 20872164 and 20821002), Chinese
Academy of Sciences and Shanghai Municipal Committee of
Science and Technology (Grant No. 07JC14063).
8 H. Ott, U. Pieper, D. Leusser, U. Flierler, J. Henn and D. Stalke, Angew.
Chem., Int. Ed., 2009, 48, 2978and references therein.
9 (a) P. G. Hayes, W. E. Piers, L. W. M. Lee, L. K. Knight, M. Parvez,
M. R. J. Elsegood and W. Clegg, Organometallics, 2001, 20, 2533;
(b) A. L. Kenward, W. E. Piers and M. Parvez, Organometallics, 2009,
28, 3012; (c) Z. Hou, Y. Luo and X. Li, J. Organomet. Chem., 2006,
691, 3114.
´
10 E. B. Lobkovskii, G. L. Soloveichik, B. M. Bulychev and A. B. Erofeev,
Notes and references
J. Struct. Chem., 1984, 25, 151.
1 (a) H. Schumann, J. A. Meese-Marktscheffel and L. Esser, Chem. Rev.,
1995, 95, 865; (b) S. Arndt and J. Okuda, Chem. Rev., 2002, 102, 1953;
11 S. Li, D. Cui, D. Li and Z. Hou, Organometallics, 2009, 28,
4814.
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3952–3958 | 3957
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12 P. B. Hitchcock, M. F. Lappert and S. Tian, J. Chem. Soc., Dalton
16 G. M. Sheldrick, SADABS, An Empirical Absorption Correction
Program for Area Detector Data, University of Goettingen, Germany,
1996.
Trans., 1997, 1945.
13 X. H. He, Y. Z. Yao, X. Luo, J. Zhang, Y. Liu, L. Zhang and Q. Wu,
Organometallics, 2003, 22, 4952.
17 G. M. Sheldrick, SHELXS-97, University of Goettingen, Germany,
14 M. F. Lappert and R. Pearce, J. Chem. Soc., Chem. Commun., 1973,
1997.
126.
18 SMART Version 5.628, Bruker Asx Inc.
19 SAINT + Version 6.22a, Bruker Axs Inc.
20 SHELXTL NT/2000, Version 6.1.
15 D. C. Bradley, J. S. Ghotra and F. A. Hart, J. Chem. Soc., Dalton Trans.,
1973, 1021.
3958 | Dalton Trans., 2010, 39, 3952–3958
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The Royal Society of Chemistry 2010
©